Actually there are two guitars, one playing the melody, the other one playing the
bassline. In these tabs I arranged to play both parts with one guitar, so you have the bass
line combined with the riff. The riff is played palm-muted and with an intensive delay, 
that repeats the tone just one time. You should listen to the song, so you can tap out the
delay time (quite short).
In the refrain you can play power chords, but without delay.

Riff

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